Amir Khan tonight suffered the first defeat of his professional career with a stunning 54-second knockout by Colombian Breidis Prescott at the MEN Arena in Manchester.

Making his debut as a pay-per-view fighter, the 2004 Olympic lightweight silver-medalist needed to impress as he pushed for a world title challenge within the next 12 months.

But those lofty ambitions were obliterated in stunning fashion as dangerous puncher Prescott overwhelmed him in the first seconds of the fight to floor him twice and record a sensational upset victory.

Khan recently replaced trainer Oliver Harrison with Miami-based former Cuban Olympic coach Jorge Rubio, putting particular emphasis on improving his defence after being floored by Michael Gomez in his last fight and previously by Willie Limond and Rachid Drilzane.

And those new defensive tactics looked set to be immediately tested by the dangerous-looking Prescott, who arrived from Barranquilla with an unbeaten record of 17 knockouts in 19 wins - albeit against opponents of a questionable standard.

Khan, 21, the current Commonwealth lightweight champion, was conceding height and natural weight advantage against an opponent used to campaigning at light-welterweight in previous fights.

He rushed straight out upon the first bell and landed his trademark short, sharp jabs and hooks.

But Prescott fired back unabashed to keep Khan at bay as the pair traded in the first few moments.

The lanky Colombian produced a punishing left hook that left Khan wobbly on his feet before another sent the Lancastrian crashing to the canvas.Even after regaining his feet, Khan was unstable and could have been stopped by referee Terry O'Connor.

And when Prescott steamed in again immediately, Khan was caught by a brilliant left hand that saw him sprawling backwards and back on the floor.This time he was unable to beat the count, leaving his world title dreams in tatters.